N-(phosphonacetyl)-L-aspartate induces TAp73-dependent apoptosis by modulating multiple Bcl-2 proteins: potential for cancer therapy.

p53 is essential for the cellular responses to DNA damage that help to maintain genomic stability. However, the great majority of human cancers undergo disruption of the p53-network. Identification and characterization of molecular components important in both p53-dependent and -independent apoptosis might be useful in developing novel therapies for cancers. In the complete absence of p53, cells treated with N-(phosphonacetyl)-L-aspartate (PALA) continue to synthesize DNA slowly and eventually progress through S-phase, suffering severe DNA damage that in turn triggers apoptosis, whereas cells with functional p53 undergo growth arrest. In this study, we investigated apoptotic signaling in response to PALA and the role of p53 expression in this pathway. We found that treatment of cells lacking p53 with PALA induced TAp73, Noxa and Bim and inactivation of these proteins with dominant-negative plasmids or small interfering RNAs significantly inhibited apoptosis, suggesting that PALA-induced apoptosis was mediated via TAp73-dependent expression of Noxa and Bim. However, PALA treatment inhibited the expression of ΔNp73 only in cells lacking p53 but not in cells expressing p53. In addition, PALA treatment inhibited Bcl-2, and overexpression of Bcl-2 significantly inhibited PALA-induced apoptosis. Moreover, expression of p53 in these cells protected them from PALA-induced apoptosis by activating p21, sustaining the expression of ΔNp73 and inhibiting the induction of Noxa and Bim. Taken together, our study identifies novel but opposing roles for the p53 and TAp73 in the induction of Noxa and Bim and regulation of apoptosis. Our data will help to develop strategies to eliminate cancer cells lacking p53 while protecting normal cells with wild-type p53.

L-Arginine reverses radiation-induced immune dysfunction: the need for optimum treatment window.

The aim of the present study was to investigate the protective efficacy of l-arginine in mitigating the injury induced by 2 Gy of total-body gamma radiation (TBI). Mice exposed to radiation (TBI group) had significantly decreased spleen weight, splenocyte numbers and bone marrow cellularity. Administration of l-arginine 2 h after TBI (TBI + l-arginine group) was effective in reducing the radiation-induced depletion of spleen and bone marrow cellularity but was not effective when administered before TBI (l-arginine + TBI group). The radiation-induced decrease in Con A-induced spleen cell proliferation, specific antibody response of spleen B cells to sheep red blood cells, and spleen RNA content was reversed in mice in the TBI + l-arginine group. The radiation-induced increase in serum TNF-alpha levels, serum nitrate/nitrite (NOx) levels, spleen DNA fragmentation, spleen nitric oxide synthase (NOS) activity, spleen inducible NOS (iNOS) activity, and hepatic iNOS activity was reversed in mice in the TBI + l-arginine group. l-Arginine administered before TBI could not reverse these changes. Mice in the TBI + l-arginine group had significantly increased spleen arginase activity compared to mice from either the TBI or l-arginine + TBI group. The results suggest the importance of the time of administration of l-arginine and the l-arginine pathway in mitigating the radiation-induced host immune dysfunction.

Role of tumor-derived transforming growth factor-beta1 (TGF-beta1) in site-dependent tumorigenicity of murine ascitic lymphosarcoma.

An ascitic lymphosarcoma (LS-A) of Swiss mice that regressed spontaneously on subcutaneous (s.c.) transplantation was investigated for the mechanism of its progressive growth and host mortality on intraperitoneal (i.p.) transplantation. In vitro studies indicated significant inhibition of LS-A proliferation seeded at higher cell density (>10(4)/ml). Culture supernatants of LS-A caused bi-modal growth effects, the early supernatants (24 h) caused stimulation and the late (72 h) supernatants inhibited LS-A proliferation. The 72-h supernatants also suppressed T and B cell response to mitogens in a dose-dependent manner. Pan anti-transforming growth factor-beta antibody abrogated the inhibitory effects of supernatants. The supernatants contained both latent as well as bio-active form of transforming growth factor-beta1 (TGF-beta1) as determined by ELISA. Mice bearing i.p. ascites tumor had elevated serum TGF-beta1, hemoglobulinemia, splenic lymphopenia, impaired response of the T cells to mitogen and reduced expression of transferrin receptor (CD71) on the bone marrow cells. However, mice which rejected s.c. transplants, did not show significant changes in these parameters. Our studies indicated profound influence of site of tumor growth on tumor progression and host immune system mediated by tumor-derived TGF-beta1. It is possible that human tumors which secrete TGF-beta1 may exhibit similar patho-physiological effects in the host depending on the anatomical site of the tumor.

Preparation and in vitro evaluation of radioiodinated bakuchiol as an anti tumor agent.

Bakuchiol, extracted from the plant Psoralea corylifolia, has been proven to have anti-tumor, cytotoxic, anti-microbial and anti-inflammatory activity. In order to study if radiolabeled bakuchiol exhibits enhanced cytotoxicity, bakuchiol was radiolabeled with 125I. In-vitro uptake studies of 125I-bakuchiol were carried out using LS-A (lymphosarcoma) and barcl-95 (radiation-induced thymic lymphoma) ascitic and solid tumor cells of murine origin. In both LS-A and barcl-95, 125I-bakuchiol showed significant uptake. Viability studies showed that the radioiodinated compound showed greater cytotoxic effect than bakuchiol.

Effect of chronic morphine administration on glucose tolerance and insulin binding to isolated rat adipocytes.

Morphine addiction was induced in six male Wistar rats. Improved glucose tolerance (peak value less by 28%, p<0.01) was observed in chronically morphinized rats as compared to the control rats, injected with saline. An increase in the maximal specific binding of 125I-labeled insulin to unit membrane area of adipocytes was observed in the experimental group (p < 0.01). The changes in insulin receptor number could be responsible for the improved glucose tolerance observed during morphine addiction.

Studies on the immunomodulatory effects of Boerhaavia diffusa alkaloidal fraction.

The alkaloidal fraction of Boerhaavia diffusa was studied for its effect on cellular and humoral functions in mice. Oral administration of the fraction (25-100 mg/kg) significantly inhibited SRBC-induced delayed hypersensitivity reactions in mice. However, the inhibition was observed only during post-immunisation drug treatment, while no effect during pre-immunisation drug treatment was observed. A significant dose-related increase in antibody titre was observed during pre- and post-immunisation treatment. The alkaloidal fraction failed to show any blastogenic responsiveness of murine splenocytes to Concanvalin A (Con A) and lipopolysaccharide (LPS). Similarly, it did not display any mitogenic activity. Thus, the present study has shown the in vivo immunostimulatory activity of B. diffusa alkaloidal fraction without an in vitro effect.

Adoptive immunotherapy of murine lymphosarcoma: comparative study using allo-immune or tumor-immune T cells.

The antitumor effect of allosensitization with lymphocytes and skin graft of DBA/2 mice was evaluated using immunogeneic, transplantable Lymphosarcoma (LS-A) syngeneic to Swiss mice. A dose dependent tumor inhibitory effect in terms of tumor free mice was observed in mice sensitized i.p. with lymphocyte doses between 10-100 million per animal. Sensitization with allogeneic primary skin graft was more effective than lymphocyte immunization. The antitumor immunity could be adoptively transferred in syngeneic Swiss mice using either allo-immune or tumor-immune T cells. Analysis of T cell phenotypes using monoclonal antibodies against cell surface markers CD4 and CD8, indicated absolute dependence on the CD4+ T cells subset in tumor cure in case of allo-immune as well as tumor-immune T cells. CD8+ T cell subset was found essential only in case of allo-immune T cell therapy. Immunosuppression of mice with whole body gamma irradiation (4 Gy), 6 hr before transfer of allo-immune or tumor-immune T cells did not abrogate the therapeutic ability of allo-immune or tumor-immune T cells. Our results suggest that allosensitization could be an effective method of generating effector lymphocyte populations that might be used to treat tumors that exhibit detectable immunogenecity.

Antituberculosis treatment-induced hepatotoxicity: role of predictive factors.

Antituberculosis drug-induced hepatotoxicity is quite common. However, factors predicting its development are still controversial. The objective of the present study was to evaluate the role of certain factors (age and sex of the patient, alcoholism, chronic liver disease, hepatitis B virus carrier status, acetylator status, nutritional status and antituberculosis treatment (ATT) regimen) in predicting the development of ATT-induced hepatitis. In a case-control study, 60 consecutive patients with evidence of ATT-induced hepatitis were studied to assess the possible association of the above-mentioned factors with ATT-induced hepatitis. Body mass index was found to be significantly lower in ATT-induced hepatitis patients (17.2 +/- 2.7) than in controls (19.5 +/- 3.3) (p < 0.05). Pyrazinamide was used in addition to isoniazid and rifampicin in a significantly higher percentage of patients in the ATT-induced hepatitis group (70%) as compared with those in the control group (42%). No significant differences were observed between the two groups with regard to the rest of the parameters.

Anti tubercular treatment induced hepatotoxicity: does acetylator status matter?

Anti tubercular drug related hepatotoxicity is common. The mechanism of injury and factors predisposing to its development are not fully understood. Forty patients with anti tubercular drugs related hepatotoxicity were studied to see the clinical and biochemical profile of these patients and to find out the significance of acetylator phenotype in the development of hepatotoxicity. Mean age of patients with liver damage (37.82 +/- 10.0 years) was similar to those without liver damage (36.48 +/- 12.5 years). Pyrazinamide appeared to increase the hepatotoxicity of isoniazid and rifampicin. The percentage of rapid acetylators and slow acetylators among patients with hepatotoxicity (70% and 30% respectively) was similar to controls (66.6% rapid and 33.3% slow acetylators). Acetylator phenotype probably has no role in anti tubercular drugs induced hepatotoxicity.

Effect of multigeneration alcohol feeding on murine immune system.

Mice belonging to F8, F12, F14 and F20 generation of a multigeneration study reared on 20% (v/v) ethanol in water as the sole drinking source were investigated for their immune competence using various parameters. The results indicated lack of any significant effect on delayed type hypersensitivity to dinitro fluorobenzene (DNFB) or sheep red blood cells (SRBC) in mice consuming ethanol. Further, alloskin graft and tumor graft response was similar in both ethanol and water fed mice. Humoral response to SRBC was also intact. However, NK cell activity was reduced significantly in ethanol fed mice. Phagocytic index as assessed by the carbon clearance test was also reduced considerably in mice consuming ethanol. The results clearly indicate that ethanol per se has a significant effect on the nonspecific limb of the immune system, in chronically fed mice.

Allosensitization induced suppression of various murine tumors: role of non-H-2 antigens in antitumor immunity.

Presence of alloantigens on various murine tumors was tested by tumor rejection in allosensitized Swiss mice. The results indicated the presence of alloantigen on immunogenic tumors like chemically induced fibrosarcoma (FS), ascitic sarcoma 180 (S 180) and immunogenic variant of lymphosarcoma (LS-A) in Swiss mice, while these antigens could not be detected by this procedure on spontaneous lymphosarcoma (LS). Allosensitization with skin graft was found to offer quantitatively higher antitumor resistance than the allosensitization achieved by allogeneic lymphocytes. Antitumor effect was not seen when tumor cells were inoculated earlier than day 3 of grafting. Further, host immunosuppression with whole body irradiation up to day of 3 of skin grafting abrogated the antitumor effect. H-2 compatible and non-H-2 incompatible skin graft sensitization of host could offer resistance against both S 180 and LS-A. Further, tumor immune mice rejected H-2 compatible, non-H-2 incompatible skin graft significantly earlier.

Antitumor immunity. II. Viability, tumorigenicity, and immunogenicity of neuraminidase-treated tumor cells: effective immunization of animals with a tumor vaccine.

A dimethylbenzdithionaphthene (DBDN)-induced fibrosarcoma showed reduced transplantability if previously treated with Vibrio cholerae neuraminidase (VCN). However, the reduced transplantability of VCN-treated tumor cells was not associated with any loss of their viability or tumorigenic capability, but appeared to be due to their increase in immunogenicity. High doses of VCN-treated tumor cells could grow even in normal individuals. Lower doses, which did not induce tumor development in normal individuals, did so if injected into immunosuppressed animals. Although X-irradiation of VCN-treated tumor cells reduced their tumorigenic potential, it did not impair their increased immunogenic properties. Thus a suitable method for the preparation of a "tumor vaccine" was provided. The immunization of animals with the vaccine and a working hypothesis regarding its mechanism of action were described.